1. Field of the Invention
The present invention relates to a method of producing a nozzle plate including a nozzle for ejecting ink, and also to such a nozzle plate.
2. Description of the Related Art
An ink jet head includes a nozzle plate formed with nozzles, and ejects ink from the nozzles onto a recording medium to perform a printing process. In the case where the peripheral portion of ink ejection ports of the nozzles has poor water repellency (ink repellency) and gets wetting with ink, the ink may adhere to the peripheral portion of the ink ejection ports and remain there. Furthermore, the ejected ink interfere with the ink adhering to the peripheral portion of the ink ejection ports to lower the ink impact accuracy. Therefore, a water-repellent film which can improve the water repellency is formed on the surface (the ink ejection side) of a substrate of the nozzle plate. Various methods of forming such a water-repellent film on the surface of a substrate have been proposed. Among the proposed methods, one method, after nozzles are formed in a substrate, masks ejection ports of the nozzles with a heat curable or photocuring resin, and then forms a water-repellent film on the resin (for example, see JP-A-Hei.6-246921 (pages 2-4; and FIGS. 1-4) and JP-A-Hei.9-131880 (pages 4-5; and FIGS. 2-3)).
In the water-repellent film forming method disclosed in JP-A-Hei.6-246921, first, a photocurable photosensitive resin film is pressure bonded to the front face of the substrate in which the nozzles are formed, to cause a part of the photosensitive resin film to enter the nozzles. Next, the substrate is irradiated from the rear face side with ultraviolet rays to cure the photosensitive resin film in the nozzles, whereby plug members are formed in the nozzles. With utilizing diffraction, refraction, and diffuse reflection of rays reaching the front face of the substrate through the nozzles, also the portion in the periphery of the ink ejection ports expanding radially outward from the ink ejection ports of the nozzles is cured in the photosensitive resin film on the front face of the substrate, to form an expanded portion having a diameter, which is larger than the inner diameter of the nozzles.
Furthermore, a photocurable photosensitive resin agent is applied to both the front face and rear face of the substrate, and the rear face is irradiated with light to cure the photosensitive resin agent on the rear face. The photosensitive resin film and the photosensitive resin agent, which have not been irradiated and remain on the front face of the substrate, are removed away by a solvent. At this time, the expanded portion on the substrate surface and a lining portion formed by the curing of the photosensitive resin agent on the rear face prevent the plug members from dropping off from the nozzles. In the state where the ink ejection ports of the nozzles are masked with the expanded portion and the plug member, a water-repellent film is formed on the surface of the substrate by water-repellent plating. Thereafter, the plug member, the expanded portion, and the lining portion are dissolved with solution to be removed away.
In the water-repellent film forming method disclosed JP-A-Hei.9-131880, first, a photocurable photosensitive resin film is attached to the rear face of a substrate in which nozzles are formed. The photosensitive resin film is heated and softened, so that the nozzles are filled with the photosensitive resin. The tip end face of the filling photosensitive resin is flattened, and made substantially flush with the front face of the substrate. The photosensitive resin film in the nozzles are exposed and cured, and a water-repellent film is then formed on the surface of the substrate by nickel plating. Thereafter, the photosensitive resin is removed away by a solvent.